Fire resistant hydraulic fluid and lubricant compositions



United States Patent Oce 3,432,437 Patented Mar. 11, 1969 3,432,437 FIRE RESISTANT HYDRAULIC FLUID AND LUBRICANT COMPOSITIONS Donald H. Nail, Los Angeles, Calif., assignor, by mesne assignments, to McDonnell Douglas Corporation, Santa Monica, Calif., a corporation of Maryland No Drawing. Filed Jan. 24, 1966, Ser. No. 522,415 U.S. Cl. 25278 10 Claims Int. Cl. C09k 3/02, 3/28 ABSTRACT OF THE DISCLOSURE Fire resistant fluids, useful as hydraulic fluids and heat transfer media, having improved liquid range and low temperature characteristics, e.g., viscosity and pour point, which comprise a mixture of a phosphate ester, a chlorinated diphenyl ether and a chlorinated biphenyl.

This invention relates to new and improved compositions particularly useful as fire resistant hydraulic fluids and lubricants of high thermal stability and good lubricity and having improved liquid range and low temperature characteristics, for example, as regards viscosity and pour point.

Various fluids have been developed heretofore having various combinations of properties required for hydraulic fluids employed for a variety of purposes. However, for many purposes highly fire resistant hydraulic fluids and lubricants are required. Thus, for example, fire resistant and explosion resistant fluids are particularly useful in high pressure systems such as in the hydraulic systems of die casting machines, hydro electric turbines, hydraulic presses, and the like, which would result in fire and explosion from leaking hydraulic fluids in the event such fluids are not adequately fire resistant.

In U.S. Patent 3,136,726 there is described a fire resistant hydraulic fluid and lubricant comprising a mixture of certain phosphate esters, e.g., a triaryl phosphate such as tricresyl phosphate, and a chlorinated biphenyl, and which may also contain viscosity improvers such as a polyalkyl methacrylate. Although these mixtures provide excellent fire resistant and explosion-proof hydraulic fluids and lubricants, they have limited application at temperatures of the order of about F. and below, because of their relatively high viscosity characteristics and tendency to crystallize out or form solids at such reduced temperatures.

In my copending application Ser. No. 408,753 filed Nov. 4, 1964, there is described an improved fire resistant hydraulic fluid and lubricant having improved low temperature characteristics, comprising a mixture of certain phosphate esters, e.g., a triaryl phosphate, and a chlorinated diphenyl ether.

I have now found that mixtures of phosphate esters, particularly triaryl phosphates such as tricresyl phosphate, with the combination of a chlorinated diphenyl ether and a chlorinated biphenyl, preferably in certain proportions noted below, provide highly improved fire resistant compositions particularly useful as hydraulic fluids and lubricants, which have good lubricity over a wide range of applied loads, good pump life when employed in a hydraulic system, good physical and chemical stability, good thermal and hydrolytic stability and noncorrosiveness, and particularly,'have improved low temperature characteristics including low viscosity at low temperatures of the order of 0 F., and below, and low pour point and cloudpoint, permitting the composition to remain liquid at such low temperatures and substantially without crystallization of solids therefrom at such temperatures. To such mixture of phosphate ester, chlorinated diphenyl ether and chlorinated biphenyl, there can be added optronally and in some instances, preferably, minor amounts of suitable viscosity improvers such as polyalkyl methacrylates, and also inhibitors, as Well as additives to enhance lubricity.

By employing a blend of a chlorinated diphenyl ether and a chlorinated biphenyl with a phosphate ester base stock according to the invention, fluids of wide versatility can be formulated tailored to the particular requirements. Thus, by selecting a particular chlorinated diphenyl ether for use in conjunction with a particular chlorinated biphenyl and a particular phosphate, e.g., tricresyl phosphate, and by selection of proper proportions of each of the three components, particularly within the ranges of such components noted below, the particular balance of high fire resistance, liquid range, and minimum viscosity and pour point of the desired fluid can be achieved. Particularly, by controlling the chlorine content of the respective chlorinated diphenyl ether and chlorinated biphenyl, and also by employment of mixtures or isomers of these respective components, fire resistance and viscosity at low temperatures, as well as the overall liquid range of the fluid composition, can be controlled.

One of the essential components of the three component fluid compositions of the invention are the phosphates. Phosphate esters suitable for use in the invention are the trialkyl phosphates, triaryl phosphates, diarylalkyl phosphates and dialkylaryl phosphates. Such phosphate esters have the general formula 0R R'Ol =O wherein R, R and R" are each a radical selected from the group consisting of phenyl, cresyl, xylyl, and an alkyl radical of from about 4 to about 12 carbon atoms, preferably from about 4 to about 10 carbon atoms. Thus, such alkyl groups can be straight or branched chain alkyl, e.g., butyl, isobutyl, pentyl, hexyl, 2-ethyl butyl, Z-ethyl hexyl, n-octyl, nonyl, decyl, and the like. Suitable phosphate esters according to the invention are, for example, tri-nbutyl phosphate, tri(2-ethylhexyl) phosphate, tricesyl phosphate, cresyl diphenyl phosphate, triphenyl phosphate, dihexyl phenyl phosphate, butyI-Z-ethylhexyl phenyl phosphate, di-(2-ethylhexyl)phenyl phosphate, butyl diphenyl phosphate, hexyl diphenyl phosphate, 6- methyl heptyl diphenyl phosphate, and the like. Triaryl phosphates such as tricesyl phosphate and cresyl diphenyl phosphate are preferred phosphates.

Suitable chlorinated diphenyl ethers which can be employed as the second essential component of the invention composition or fluid can include from about 1 to about 10 chlorine atoms in the molecule, generally from about 1 to about 6 chlorine atoms per molecule. In each instance, the monodi-, tri-, tetra-, penta-, and hexa-chloro derivatives of the diphenyl ether according to the invention, consist primarily or substantially entirely of substitution chlorine on the aromatic rings, rather than addition chlorine, and in each case the ether used can be either a particularly selected isomer or compound, or mixture of isomers, or an unresolved mixture of isomers or mixture of chlorinated ethers of varying numbers of chlorine atoms in the molecule. Such mixtures of chlorinated diphenyl ethers are obtained from the reaction of chlorine with diphenyl ether, e.g., as described in U.S. Patents 2,022,632 and 2,165,813.

Compositions of the invention particularly having reduced viscosity are prepared employing chlorinated diphenyl ethers preferably having from about 1 to about 4 chlorine atoms per molecule. In some instances where it is particularly desired to provide compositions according to the invention which are useful as low viscosity coolants, such compositions are prepared using as a chlorinated diphenyl ether component a mixture which can also include, for example, some unchlorinated diphenylether as well as, for example, monochloro and dichloro diphenyl ethers. For general purpose wide utility, mixtures of chlorinated diphenyl ethers averaging, for example, about 4 chlorine atoms per molecule can be employed. Thus, for example, the term tetrachloro diphenyl ether employed herein refers to either the specific tetrachlorinated derivative or a mixture of chlorinated diphenyl ethers which averages approximately 4 chlorine atoms per molecule and consisting of mixtures of the various isomer molecules chlorinated to varying degrees.

The combined chlorine content of the preferred chlorinated diphenyl ethers employed in the invention composition can range from about 15 to about 59% by weight, encompassing such ethers which contain from about 1 to about 6 chlorine atoms, preferably from about 15 to about 50% corresponding to such ethers containing the preferred about 1 to about 4 chlorine atoms. The combined chlorine content of the mixture of chlorinated diphenyl ethers containing an average of about 4 chlorine atoms per molecule can range from about 45 to about 50% by weight.

The chlorinated biphenyls suitable for use as the third essential component of the fluid composition of the invention are those which contain from about 1 to about chlorine atoms per molecule. Here also, as in the case of the chlorinated diphenyl ether component, the respective mono-, di-, tri-, tetra-, and penta-chloro derivatives of biphenyl according to the invention, consist primarily or substantially entirely of substitution chlorine on the aromatic rings, rather than addition chlorine, and in each case the chlorinated biphenyl employed can be either a particularly selected isomer or compound, or mixture of isomers, or an unresolved mixture of isomers or mixture of chlorinated byphenyls of varying numbers of chlorine atoms in the molecule. Thus, for example, the term tetrachloro biphenyl employed herein refers to either the specific tetrachlorinated derivative or a mixture of chlorinated biphenyls which averages approximately 4 chlorine atoms per molecule and consisting of mixtures of the various isomer molecules chlorinated to varying degrees. Such chlorinated biphenyls can be obtained by the reaction of chlorine with biphenyl, in a manner known in the art. Preferred biphenyls for use as the third component of the fluids of the invention are those having from about 3 to about 5 chlorine atoms per molecule.

The combined chlorine content of the chlorinated biphenyls containing from about 1 to about 5 chlorine atoms can range from about 18 to about 55%. The preferred chlorinated biphenyls containing from about 3 to about 5 chlorine atoms are those having from about 40 to about 55% combined chlorine. Suitable chlorinated biphenyls are available in the trade; for example, they are made and sold under the trademark designation Aroclor. In terms of the trademark designation, Aroclor 1242, Aroclor 1248, and Aroclor 1254 are preferred for the compositions of this invention. These Aroclor chlorinated biphenyls contain about 42%, 48% and 54% by weight of combined chlorine, respectively, and also correspond approximately to the tri-, tetra-, and penta-chlorobiphenyls, respectively.

The proportion of phosphate ester to the sum or the blend of the chlorinated diphenyl ether and chlorinated biphenyl components can vary widely, e.g., over a range of about 20 to about 80% of phosphate ester and about 80 to about 20% of the sum of the two chlorinated components, by weight. The three component fluid composition of the invention should contain at least of the chlorinated diphenyl ether and at least 10% of the chlorinated biphenyl. In preferred practice, useful three component fluids according to the invention are obtained employing about 30% to about 70% phosphate ester or a mixture of phosphate esters, and about 70 to about 30% by weight of the sum of the two chlorinated components. Preferably, the relative proportions of chlorinated diphenyl ether and chlorinated biphenyl are such that the mixture of the two chlorinated components contains from about 30 to about 70% of chlorinated diphenyl ether and about 70 to about 30% of chlorinated biphenyl. All of the proportions noted above are weight proportions,

Although the otherwise unsubstituted phosphate esters described above are preferred for use in the invention composition, substituted trialkyl, triaryl, alkyl diaryl and dialkylaryl phosphate esters, e.g., chlorine substituted phosphate esters of this type, can also be employed and are included within the definition of the suitable phosphate esters set forth above. Thus, for example, R, R and R" in the formula above include chloroalkyl or chlorophenyl, e.g., 0-, por rn-chlorophenyl. Any of the phosphate esters described above can be employed separately, or mixtures thereof can be employed in the fluid compo sition of the invention.

The use of a combination of chlorinated diphenyl ether and chlorinated biphenyl together with the phosphate ester in the three component fluid compositions of the invention, have important advantages over the use of a chlorinated biphenyl alone or a chlorinated diphenyl ether alone, with the phosphate ester. Thus, the use of mixtures or blends of the chlorinated diphenyl ether and chlorinated biphenyl generally have a substantially lower viscosity than the corresponding chlorinated biphenyls of equivalent chlorine content, and accordingly reduce the viscosity of the phosphate-containing fluid. Although the chlorinated diphenyl ethers or chlorinated diphenyl oxides often contain high melting constituents which tend to separate out as solids, e.g., at room temperature, and below, addition of suflicient chlorinated biphenyl to the chorinated diphenyl ether unexpectedly retards this tendency so that useful fluids containing phosphate esters and such chlorinated components can be formulated. Thus, the resulting fluids of the invention have lower viscosity, a greater degree of fire resistance for a given chlorine content of chlorinated diphenyl ether and chlorinated biphenyl components, and a wider dependable liquid range than a fluid containing the same proportion of chlorinated biphenyl of comparable chlorine content employed alone, or a fluid containing a corresponding proportion of chlorinated diphenyl ether of corresponding chlorine content, employed alone.

Thus, the three component fluid formulations of the invention containing a combination of chlorinated diphenyl ether and chlorinated biphenyl can be provided having extremely high fire resistance, on the one hand, and, for example, where it is necessary to provide fluids of good viscosity at low temperature which can flow readily, e.g., as a compressor lubricant on a cold day, invention fluids can be formulated or tailored to solve such problem, or at a given viscosity to provide fluids with improved fire resistance.

As previously noted, viscosity index improvers can be incorporated in the invention compositions, although not necessarily. Thus, to a mixture of phosphate ester and chlorinated diphenyl ether and chlorinated biphenyl, according to the invention, can be added suitable polyalkyl methacrylates, e.g., those marketed as Acryloid. These materials have varying molecular weight and viscosity. In general, the polymerized alkyl methacrylates suitable for use in the invention composition or fluid contain from about 2 to about 18, preferably about 4 to about 10 carbon atoms in the alkyl group, and have a molecular weight within the range of about 2,000 to about 20,000 and an average molecular weight Within the range of about 3,000 to about 15,000. Usually a minor proportion, e.g., about 0.2 to about 10% by weight, of such polyalkyl methacrylate is employed.

The following are examples of practice of the invention:

EXAMPLE 1 The following are blends or mixtures of triaryl phosphates, chlorinated diphenyl ethers, and chlorinated biphenyls according to the invention:

TABLE I Percent by weight (1) Monochlorodiphenyl ether 25 Pentachlorobiphenyl 25 Tricresyl phosphate 50 (2) Tetrachlorodiphenyl ether 25 Tetrachlorobiphenyl 25 Tricresyl phosphate 50 (3) Pentachlorodiphenyl ether 25 Pentachlorobiphenyl 25 Tricresyl phosphate 50 (4) fletrachlorodiphenyl ether 25 Pentachlorobiphenyl 25 Tricresyl phosphate 50 (5) Hexachlorodiphenyl ether 25 Tetrachlorobiphenyl 25 Tricresyl phosphate 50 (6) Trichlorodiphenyl ether l5 Pentachlorobiphenyl Tricresyl phosphate 50 (7) Trichlorodiphenyl ether 15 Tetrachlorobiphenyl 35 Tricresyl phosphate 50 (8) Tetrachlorodiphenyl ether 17 Pentachlorobiphenyl 17 Pentachlorodiphenyl ether 17 Tricresyl phosphate 49 Blends 1 to 8 above are illustrative of the large number of blends or formulations of fluid compositions according to the invention which can be formulated. The formulations of higher chlorine content are particularly highly fire resistant and the compositions of lower chlorine content tend toward lower viscosity at decreased temperatures. Composition 8 illustrates formulations which contain more than one component of the class of chlorinated diphenyl ethers. Blends of this type are desirable to provide greater versatility in achieving the liquid range and viscosity required in a particular case.

Fluid formulations corresponding to compositions 1 to 8 of Table I above can be used as hydraulic fluids or lubricants in industrial air compressors, hydraulic presses, hydroelectric turbines, and the like.

EXAMPLE 2 The following are additional examples of fire resistant fluid formulations according to the invention:

TABLE II Percent by weight (9) Cresyl diphenyl phosphate Dichlorodiphenyl ether 35 Tetrachlorobiphenyl 25 (10) Di(2-ethyl hexyl)phenyl phosphate 60 Tetrachlorodiphenyl ether 30 Trichlorobiphenyl 10 (11) Butyl diphenyl phosphate 70 Pentachlorodiphenyl ether 10 Tetrachlorobiphenyl 20 (12) Dibutyl phenyl phosphate 55 Pentachlorodiphenyl ether 25 Pentachlorobiphenyl l5 Tetrachlorobiphenyl 5 (l3) Di(Z-ethyl hexyl)phenyl phosphate 50 Tetrachlorodiphenyl ether 30 Tetrachlorobiphenyl 10 A mixture of 30% by weight of a poly n-butyl methacrylate having an average molecular weight of 7,900 and 70% by weight of an organic phosphate ester as a carrier and solvent; marketed as Acryloid R-3876X 10 Percent by weight (14) Hexyl diphenyl phosphate 45 Hexachlorodiphenyl ether 30 Tetrachlorobiphenyl 25 (15) Diphenyl m-chlorophenyl phosphate 65 Trichlorodiphenyl ether 20 Tetrachlorobiphenyl 15 The above formulations 9 to 15 of Table II further illustrate the improved hydraulic fluid and lubricant compositions of the invention containing various types of phosphate esters in varying proportions, and various blends of chlorinated diphenyl ethers and chlorinated biphenyls, employed in conjunction with such phosphates.

Here again, the relative fire resistance, liquid range and viscosity characteristics at low temperature will vary chiefly in relation to the degree of chlorination of the chlorodiphenyl ether and chlorobiphenyl components and the relative proportions of these components with respect to each other and with respect to the phosphate ester. All of these formulations have utility as industrial hydraulic fluids for use in hydraulic presses and turbines, and as industrial lubricants, for example, in compressors, and the like. From the foregoing, it is seen that the invention provides novel and improved fluid compositions particularly useful as hydraulic fluids, lubricants, coolants and the like. Mixtures according to the invention have the following characteristics.

(1) High fire resistance particularly where the chlorinated diphenyl ether and chlorinated biphenyl each contains at least 40% chlorine by weight or where a large proportion of phosphate ester is used to oifset the lower chlorine content.

( 2) Good to excellent thermal stability.

(3) Good to excellent oxidative stability.

(4) Very good lubricity.

(5) Wide liquid .range with relatively low pour point and cloud point.

(6) Improved viscosity at low temperature of the order of 0' F. and below.

(7 Compatibility with metals used in construction of hydraulic systems operating over wide temperature ranges.

8) The fluids of the invention are versatile and relative proportions of the components can be selected and varied to achieve the properties desired for the intended application.

While I have described particular embodiments of my invention for the purpose of illustration, it should be understood that various modifications and adaptations thereof may be made within the spirit of the invention, as set forth in the appended claims.

I claim:

1. A fire resistant fluid composition consisting essentially of from 20% to by weight of a phosphate ester having the general formula wherein R, R, and R are each a radical selected from the group consisting or phenyl, cresyl, xylyl, and an alkyl radical of from about 4 to about 12 carbon atoms; and from 80% to 20% by weight of the sum of a chlorinated diphenyl ether and a chlorinated biphenyl, said chlori nated diphenyl ether and chlorinated biphenyl each being present in an amount of at least 10% by weight of said composition, said chlorinated diphenyl ether having a combined chlorine content of about 15% to about 59% by weight and said chlorinated biphenyl having a combined chlorine content of from about 18% to about 55%.

2. A fire resistant fluid composition as defined in claim 1, wherein said chlorinated diphenyl ether comprises a chlorinated diphenyl ether containing in the range from about 1 to about 6 chlorine atoms per molecule, and said chlorinated biphenyl comprises a chlorinated biphenyl containing in the range from about 1 to about chlorine atoms per molecule.

3. A fire resistant fluid composition as defined in claim 1, wherein said phosphate ester has the formula wherein R, R and R" are each a radical selected from the group consisting of phenyl, cresyl, xylyl, and an alkyl radical of from about 4 to about 12 carbon atoms, and containing about 30 to about 70% by weight of said phosphate ester and about 70 to about 30% by Weight of the sum of said chlorinated diphenyl ether and said chlorinated biphenyl, said chlorinated diphenyl ether and said chlorinated biphenyl each being present in an amount of at least by weight of said composition, and wherein said chlorinated diphenyl ether comprises a chlorinated diphenyl ether containing in the range from about 1 to about 4 chlorine atoms per molecule, and said chlorinated biphenyl comprises a chlorinated biphenyl containing in the range from about 3 to about 5 chlorine atoms per molecule, said chlorinated diphenyl ether having a combined chlorine content of about to about 50%, and

said chlorinated biphenyl having a combined chlorine content of about 40 to about 55%.

4. A fire resistant fluid composition as defined in claim 1, wherein said chlorinated diphenyl ether and said chlorinated biphenyl comprises a blend containing about 30 to about 70% of chlorinated diphenyl ether and about 70 to about 30% of chlorinated biphenyl.

5. A fire resistant hydraulic fluid and lubricant as defined in claim 1, and containing about 0.2 to about 10% by weight of a polyalkyl methacrylate in which the alkyl radical has from about 2 to about 18 carbon atoms and having a molecular weight within the range of about 2,000 to about 20,000.

6. A fire resistant fluid composition as defined in claim 2, wherein said chlorinated diphenyl ether and said chlorinated biphenyl comprises a blend containing about 30 to about of chlorinated diphenyl ether and about 70 to about 30% of chlorinated biphenyl.

7. A fire resistant hydraulic fluid and lubricant as defined in claim 2, wherein said phosphate ester is tricresyl phosphate.

8. A fire resistant hydraulic fluid and lubricant as defined in claim 2, wherein said phosphate ester is cresyl diphenyl phosphate.

9. A fire resistant hydraulic fluid and lubricant as defined in claim 2, wherein said phosphate ester is di-(2- ethylhexyl)phenyl phosphate.

10. A fire resistant fluid composition as defined in claim 3, wherein said chlorinated diphenyl ether and said chlorinated biphenyl comprises a blend containing about 30 to about 70% of chlorinated diphenyl ether and about 70 to about 30% of chlorinated biphenyl.

References Cited UNITED STATES PATENTS 2,934,501 4/1960 Moreton 252-78 3,136,726 6/1964 Moreton 252--78 FOREIGN PATENTS 1,327,189 4/1963 France.

LEON D. ROSDOL, Primary Examiner.

S. D. SCHWARTZ, Assistant Examiner.

U.S. Cl. X.R. 25249.6 

